1. Field of the Invention
This invention relates to a starting motor with an intermediate gear utilized in a vehicle, particularly to rotation-blocking fixation of an intermediate shaft thereof.
2. Discussion of Background
FIG. 4 is a longitudinal sectional diagram showing a conventional starting motor with an intermediate gear. A reference numeral 1 designates a DC motor, wherein a rotating shaft 3 is extended from an armature 2 and a field pole 6 is attached to a yoke 5 of a stator 4. A numeral 7 designates a front bracket connected to the yoke 5, which supports a front end of the rotating shaft 3 through a bearing 8.
A numeral 10 designates an overrunning clutch supported by the rotating shaft 3 slidably in the axial direction, composed as follows. A numeral 11 designates a clutch outer connected to an outer periphery of the rotating shaft 3 by a helical spline 9 thereby transmitting the rotation, and 12, a clutch inner to which a one-way rotation is transmitted through rollers 13 from the clutch outer 11, which is supported by the rotating shaft 3 through a sleeve bearing 19. A pinion 14 is integrally formed at a front end of the clutch inner 12. A numeral 15 designates a clutch cover fixed to the clutch outer 11 by calking through a holding plate 16, and 17, a stop ring attached to the clutch outer 11. An engaging groove 18 is formed between the stop ring 17 and a stepped portion of the clutch outer 11. A numeral 20 designates a stopper attached to the rotating shaft which restrains a forward movement position of the overrunning clutch 10.
A numeral 21 designates a shift lever, an intermediate fulcrum of which is supported by the front bracket 7 and a receiving body 24 that is received by a grommet 22 attached to the yoke 5 through a compression spring 23, and a forked lower end of which engages with the engaging groove 18 in the axial direction. An upper end of the shift lever 21 engages with a front end of a plunger of an electromagnetic switch (not shown) of the motor 1 in the axial direction and the shift lever 21 swivels around the fulcrum.
A numeral 25 designates an intermediate shaft paralleled with the rotating shaft 3 and supported by insertion holes 7a and 7b of the front bracket 7, and 26, a grommet (composed of a gummy material) inserted into a round hole 7c provided at a back end portion of the front bracket 7 communicating to the insertion hole 7b and engaged with a front end of the yoke 5, a front end of which engages with a back end of the intermediate shaft 25 and blocks rotation thereof. A numeral 27 designates an intermediate gear supported by the intermediate shaft 25 rotatably and slidably in the axial direction, through a sleeve bearing 28 fixed to an inner periphery thereof, which meshes with the pinion 14. A numeral 29 designates a ring-like co-rotating body fixed to an outer periphery of a clutch cover 15, a flange 29a of which engages with an engaging groove 27a provided at an outer periphery of a boss of the intermediate gear 27. In accordance with the forward and backward movement of the overrunning clutch 10, the intermediate gear 27 moves forwardly and backwardly by the ring-like co-rotating body 29. A numeral 30 designates a ring-gear provided at a flywheel of an internal combustion engine, which meshes with the intermediate gear 27 by the forward movement thereof, thereby starting to rotate the engine.
FIG. 5 is an exploded view showing the grommet 26 and the intermediate shaft 25. At a back end of the grommet 26, a rotation-blocking protrusion 26b is provided which contacts a stepped outer periphery of the yoke 5 thereby blocking the rotation thereof. At a front end of the grommet 26, a protrusion 26a is provided, which engages with an engaging groove 25a at a back end of the intermediate shaft 25.
Next, explanation will be given to the operation. When current flows in an excitation coil of the electromagnetic switch, the plunger is drawn and swivels the shift lever 21 in the counterclockwise direction in FIG. 4. By this operation, the overrunning clutch 10 moves forwardly and is received by the stopper 20. By the forward movement of the overrunning clutch 10, the intermediate gear 27 moves forwardly by the ring-like co-rotational body 29 and meshes with the ring-gear 30. Next, fixed terminals of the electromagnetic switch (not shown) are closed, current flows in a circuit of the DC motor 1, the armature 2 starts rotating, the rotation of the rotating shaft 3 is transmitted to the intermediate gear 27 through the overrunning clutch 10 and the pinion 14 and the rotation is transmitted to the ring-gear 30, thereby starting up the internal combustion engine.
In the conventional starting motor with an intermediate gear, a co-rotation of the intermediate shaft 25 by the rotation of the intermediate gear 27 is blocked by the engagement with the grommet 26. However, the grommet 26 is composed of a gummy material, deformation thereof is caused, the rotation -blocking is performed insufficiently and, therefore, the durability thereof is poor. Furthermore, when the grommet 26 is made of a metallic material or a synthetic resin material, a portion of a level-difference may be caused at a portion receiving the thrust force, a play is formed in the intermediate shaft 25 and wear is generated at a thrust-receiving portion of the intermediate shaft.